Ireland's Jason Smyth meanwhile proved himself as the fastest Paralympian in history by defending his 100m and 200m double from Beijing on Friday, while Du Toit's team-mate Oscar Pistorius sought to salvage his Games after two shock defeats.

The penultimate full day of competition in London saw a number of sports reach their conclusion, with Vergeer's title never destined for anyone else given her remarkable winning streak in singles that stretches back to 2003.

"I know the day I will lose will come but I don't know when," the 31-year-old said after beating compatriot Aniek van Koot 6-0, 6-3 on the blue hardcourts of Eton Manor to take the title for the fourth time in a row.

In the Olympic Stadium, Irish sprinter Smyth showed his undisputed class by breaking his own T13 200m world record for visually impaired athletes to win in 21.05sec, less than a week after winning the 100m in another world best time.

The 25-year-old, who has the genetic condition Stargardt's disease, won the same double in Beijing four years ago, while Russia-born US wheelchair racer Tatyana McFadden took her third gold of the Games in the T54 1,500m.

Both victories came before Pistorius eased through to Saturday's final of the T44 400m for single and double below-the-knee amputees, which as the only athlete in the field who has run under 50sec, he is expected to win.

Predictions of a Pistorius victory in the sprints have gone awry in London after he lost his 100m and 200m titles in a clear sign of a shift in power away from the most recognisable face in disabled sport.

The new 100m champion, Britain's Jonnie Peacock, said the fact that all eight finalists on Thursday ran under 12sec demonstrated the improvements other athletes had made in the sport since Beijing.

"It's testament to Paralympic sport and this class as a whole," said the 19-year-old world record holder, adding that Pistorius could no longer expect to dominate amputee sprinting over a number of events.

"If Oscar goes and trains for the 400, when it comes to the 100 and 200 it's going to be harder for him to win. He's not going to have it his way like he used to," he added.

"It's all over," said the 28-year-old Du Toit, who was a promising non-disabled swimmer until 2001 when she had her left leg amputed below the knee after a scooter accident.

"I walk away with absolutely no regrets. I look back and I think I gave everything. No matter what emotions you go through I gave everything in the pool, everything as a person and I'm satisfied."

The Cape Town swimmer's story of courage in the face of a major setback has inspired millions.

Former US Navy lieutenant Brad Snyder is doing likewise, as he won the men's S11 400m freestyle gold for blind and visually impaired swimmers -- exactly a year to the day since he was blinded on the battlefields of Afghanistan.

Meanwhile, Jacqueline Freney won her eighth gold of the Games as Australia's women won the 4x100m medley 34 points relay; Brazil's Daniel Dias and Matthew Cowdrey of Australia both claimed their fifth golds.

In cycling, more road medals were decided at the Brands Hatch motor racing circuit in southeast England, with another gold for former Formula One and Indy car driver Alessandro Zanardi.

Zanardi, 45, who had both legs amputated after a horror smash in 2001, took the men's H4 time-trial over 16 kilometres on Wednesday and followed it up on Friday by taking the 64km road race in a thrilling sprint finish.

Elsewhere, Japan beat China 1-0 in the women's goalball final while Finland took men's gold with an 8-1 victory over Brazil.